Fuel oils for gas turbine engines and process of making same



Patented Mar. 20, 1951 FUEL OILS FOR GAS TURBINE ENGINES AND PROCESS OF MAKING SAME Donald Albert Howes, Sunbury-on-Thames, England, assignor to Anglo-Iranian Oil Company Limited, London, England, a British corporation No Drawing. Application November 5, 1948, Serial No. 58,597. In Great Britain November 7, 1947 The invention relates to the production of a fuel for gas turbine engines, and has among its objects to provide a fuel for gas turbine engines by the use of which the build-up of scale upon the turbine blades is eliminated or the rate of build-up greatly reduced.

In the gas turbines, fuel is injected into a combustion zone and is ignited in the presence of an excess of air, the products of combustion being directed towards turbine blades having carefully designed contours, whereby the energy of the gas stream is converted into rotary energy. The efficiency of conversion is high. Although it is desirable for various reasons to use cheap residual fuels, it has been found that the use of such fuels is severely limited by the fact that in many instances certain of the inorganic materials present in the fuel, fail to remain in the gas stream after combustion and deposit in the turbine engine to form a scale, notably on the rotor and stator blades, resulting in a decrease in the efficiency of the engine, and necessitating the shutting-down of the unit at frequent intervals for cleaning of the blades and other parts of the engine on which the scale has deposited,

It has been found that the presence of vanadium compounds in the residual fuel is largely responsible for the formation of this scale and that in orderto prevent the build-up of scale from reaching such a degree that it materially reduces the value of the fuel in its application to gas turbine engines it is necessary to reduce the vanadium content of the fuel to below 0.03% wt. and preferably to eliminate it entirely.

It is among the objects of the invention to provide a petroleum fuel, derived from a petroleum residue fraction which may have a high vanadium content, which is suitable for use as a gas turbine fuel and in which the disadvantages hereinbefore referred to are materially reduced. More particularly it is among the objects of the invention to provide a fuel for gas turbine engines, the use of which materially reduces or avoids the formation of scale upon the interior surfaces of a gas turbine engine such as upon the rotor and stator blades.

According to the invention a fuel suitable for use in gas turbine engines is obtained by a process which comprises treating a petroleum residue fraction preferably constituting not more than 30% by volume on the crude petroleum and containing at least one vanadium compound in elemental or combined form, with a solvent containing one or more hydrocarbons having 3-7 carbon atoms per molecule and thereafter separating 3 Claims. (Cl. 19614.46)

the solution so obtained from the material insoluble in the said solvent.

The solvent is preferably substantially aromatic-free and should not have an aromatic content greater than 0.5%.

The preferred hydrocarbons for use as solvent are normal hexane and normal heptane or there may be used a mixture of these hydrocarbons, or a solvent mixture containing normal hexane and/or normal heptane. Preferably the total weight of normal hexane and normal heptane in the solvent mixture constitutes at least Preferably the petroleum residue fuel is treated with at least 500% and preferably about 800% by volume of the hydrocarbon containing solvent.

By operating according to the above process, it has been found possible to remove all or a large proportion of the vanadium compounds in the residue as material insoluble in the solvent. After separation of the insoluble material, the solvent is usually stripped from the residue fraction, and the fraction thus refined, with or without blending or further treatment, is suitable for use as a gas turbine fuel.

The process of the invention is most advantageously applied to petroleum residue fractions having a total vanadium content of at least 0.03 by weight, estimated as elemental vanadium.

The invention is illustrated but in no Way lim ited by the following examples.

Example I A 12.4% by volume residue fraction derived from a Middle East crude petroleum oil was treated at room temperature with 800% by weight of petroleum ether of boiling range C. to C. The solution so formed was allowed to stand for a few hours and then the insoluble material was filtered off and the resulting solution distilled to remove the petroleum ether solvent.

Distribution of vanadium was found to be as' shown in the following table.

Parts by weight 12.4% residue from Middle East crude Material insoluble in the solvent 19.5 Vanadium content of unreacted material 0.065 Vanadium content of material insoluble in the solvent (thatis 0.22% by weight of insoluble material) 0.043 Treated residue 80.5 Vanadium content of treated residue fraction (that is 0.024% by weight of treated residue) 0.019

Thus, by the process of the invention the vanadium content is reduced from 0.065% by weight in the untreated residue to 0.024% by weight in the treated residue, the fuel so obtained being particularly suitable for gas turbines.

Example II 1 volume of a 16.7% by volume residue fraction derived from a Middle East petroleum oil and having a vanadium content of 0.012% was treated at 140 F. with 8 Volumes of a hydrocarbon solvent. Insoluble material was separated by filtration and the resulting solution distilled to remove the hydrocarbon solvent. Distribution of vanadium between treated residue and precipitate was found to be as shown by the following table based on the treatment of 100 parts by weight of residue.

at least one hydrocarbon havin 3-? carbon atoms per molecule and which has an aromatic content no greater than about 0.5%, separating the formed insoluble material from the resulting solution of treated petroleum residue fraction and solvent and finally separating the solvent from the solution to recover the desired endproduct containing a total vanadium content of below 0.03% by weight.

2. Process in accordance with claim 1 wherein the solvent employed comprises at least one hydrocarbon selected from the group consisting of normal hexane, normal heptane, and mixtures thereof, the total weight of normal hexane and normal heptane in the solvent being at least about 50% by weight; the amount of sol- Process yield, Parts by weight Vanadium Content, per cent by weight Solvent 22353: gg? Treated Residue Precipitate Propane 20.1 79. 9 0.015% of fraction, 100% of total. Butane 68. 32. 0 0.033% of fraction, 87.5% of total. Iso-butane 48. 0 52. 0 0.022% of traction, 96.2% of total. Pentane 81. 7 18. 3 0.047% of fraction, 72.3% of total. Hexane 85. 7 l4. 3 0.047% of fraction, 55.5% of total.

Example III A 25.2% by volume residue fraction derived from a Middle East crude petroleum oil and having a vanadium content of 0.030'7% by weight was treated with 8 times its volume of propane in a countercurrent tower operated at 150 F., tower top, and 110 F., tower base. The treated residue constituted 36% by weight of the feedstock and contained no vanadium.

Example IV The residue fraction described in Example III was treated batchwise with 8 times its volume of 6080 C. boiling range paraffinic petroleum ether at room temperature. The treated residue constituted 90% by weight of the feedstock and contained 0.0166% by weight of vanadium.

I claim:

1. Process for the production of a fuel oil, suitable for use in gas turbine engines, which comprises combining a petroleum residue fraction which constitutes not more than about by volume on the crude petroleum and which contains at least one vanadium compound, the total vanadium content of said fraction being at least about 0.03% by weight, with at least about 500% by volume of a solvent containing REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,002,004 Gard May 21, 1935 2,115,846 Frolich May 3, 1938 2,367,385 Weeks et a1. Jan. 16, 1945 2,409,437 La Crosse Oct. 15, 1946 OTHER REFERENCES The Science of Petroleum by Dunstan et a1., vol. II, pages 1053-1055. Pub. by Oxford University Press, London, England, 1938. 

1. PROCESS FOR THE PRODUCTION OF A FUEL OIL, SUITABLE FOR USE IN GAS TURBINE ENGINES, WHICH COMPRISES COMBINING A PETROLEUM RESIDUE FRACTION WHICH CONSTITUTES NOT MORE THAN ABOUT 30% BY VOLUME ON THE CRUDE PETROLEUM AND WHICH CONTAINS AT LEAST ONE VANADIUM COMPOUND, THE TOTAL VANADIUM CONTENT OF SAID FRACTION BEING AT LEAST ABOUT 0.03% BY WEIGHT, WITH AT LEAST ABOUT 500% BY VOLUME OF A SOLVENT CONTAINING AT LEAST ONE HYDROCARBON HAVING 3-7 CARBON ATOMS PER MOLECULE AND WHICH HAS AN AROMATIC CONTENT NO GREATER THAN ABOUT 0.5%, SEPARATING THE FORMED INSOLUBLE MATERIAL FROM THE RESULTING SOLUTION OF TREATED PETROLEUM RESIDUE FRACTION AND SOLVENT AND FINALLY SEPARATING THE SOLVENT FROM THE SOLUTION TO RECOVER THE DESIRED ENDPRODUCT CONTAINING A TOTAL VANDIUM CONTENT OF BELOW 0.03% BY WEIGHT. 